Application Of Fluid Analyses To The Operation Of An In Situ Combustion Pilot

Abstract

Abstract This paper reports the interpretation of the results from an extensive field fluids monitoring program which supported the operation of the Petro-Canada/ AOSTRA heavy oil in situ combustion pilot at Kinsella, Alberta. Produced gas analyses are discussed in terms of confirmation of reservoir ignition, monitoring the progress and efficiency of the burn, safety considerations and the extent of air propagation in the reservoir. Fireflood indicators in the produced water indicated the proximity of the/ire with respect to individual wells, as well as providing insights into the chemical processes occurring during combustion. Changes in oil composition indicated which wells were most influenced by low temperature oxidation, distillation and thermal cracking of the oil. An over-all assessment of the data, in conjunction with operational parameters, demonstrated that fireflood indicators in the produced fluids can be used over the entire pilot operation to monitor the advance of the fire/rant and to estimate the location of the fire with respect to production wells. Introduction Steam-based thermal recovery strategies have found widespread application. However, some shallow reservoirs with a thin net pay zone and containing viscous oil are currently best exploited using an in situ combustion process. Operators such as Pan Canadian Petroleum(1). Amoco(2). Husky (3), General American Oils(4), and Petro-Canada(5) have reported on the complexities of operating fireflood projects in Alberta. The Kinsella Heavy Oil In Situ Combustion Project (KHOPD) was a joint venture between Petro-Canada Resources and the Alberta Oil Sands Technology and Research Authority (AOSTRA). The pilot site was located approximately ZOO kmsoutheast of Edmonton, Alberta (Fig. I). The air pattern originallyonsisted of four air injection wells (BI-I, BI-2. BI-3 and I-4), five production wells (BP-1, BP-2, BP-3, BP-4 and BP-5) and three observation wells (BO-I, BO-2 and BO-3). The air attern was subsequently modified with the addition of three production wells (BP-6, BP-7 and BP-8) and two observation wells (BO-4 and BO-5). The four wells BP-I, BP-6, BP-7 and BP-8 essentially yielded an inverted five-spot around the air injector BI-4 (Fig. 2). The produced fluid compositions from three additional wells (AP-2, AP-4 and AP-5), located some distance from the air pattern (Fig. 2), were also monitored. Dry combustion was carried out at KHOP-D for approximately two years. The wet combustion phase commenced in August 1983 with intermittent water injection into BI-4 for the purpose of scavenging heat from the burned zone and transmitting this heat(in the form of steam) to the oil bank in front of the combustion zone. To assist with the operation of this pilot, in understanding the reservoir behaviour and in the design of subsequent projects, an extensive fluids analysis program was establishedto monitor the composition of the produced fluids. Regular sampling and analysis of produced gas, oil and water from as many as eleven production wells continued for approximately 3 and a half years. Gas and water samples were generally analyzed on a weekly basis, while oil samples were analyzed twice per month. Indications that the firefront was approaching a particular well often necessitated more frequent analysis.